imx: replace CONFIG_SECURE_BOOT with CONFIG_IMX_HAB

CONFIG_SECURE_BOOT is too generic and forbids to use it for cross
architecture purposes. If Secure Boot is required for imx, this means to
enable and use the HAB processor in the soc.

Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/board/warp7/imximage.cfg b/board/warp7/imximage.cfg
index a6edfda..a4c2f67 100644
--- a/board/warp7/imximage.cfg
+++ b/board/warp7/imximage.cfg
@@ -12,7 +12,7 @@
 #include <config.h>
 
 IMAGE_VERSION	2
-#ifdef CONFIG_SECURE_BOOT
+#ifdef CONFIG_IMX_HAB
 CSF CONFIG_CSF_SIZE
 #endif